Timing Chain Question

[Bill <Y1TopBanana73@xxxxxxxxx>]

I need to ask a stupid question...what defines a timing chain as
"double roller"? Is it that the width of the chain is 2 smaller links
wide instead of 1, and the cam & crank sprockets have rows of teeth
that are 2 wide instead of one?

Also, what makes this setup so much better/stronger than a single chain?

Thanks in advance

Bill M
65 Coronet 500 'vert